Quantifier Shift - Examples

Examples

1. Every person has a woman that is their mother. Therefore, there is a woman that is the mother of every person.

xy(Px → (Wy & M(yx))) therefore yx(Wy → (Px & M(yx)))

It is fallacious to conclude that there is one woman who is the mother of all people.

However, if the major premise ("every person has a woman that is their mother") is assumed to be true, then it is valid to conclude that there is some woman who is any given person's mother.

2. Everybody has something to believe in. Therefore, there is something that everybody believes in.

xy Bxy therefore yx Bxy

It is fallacious to conclude that there is some particular concept to which everyone subscribes.

It is valid to conclude that each person believes a given concept. But it is entirely possible that each person believes in a unique concept.

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